<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>方向箭头</title>
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        integrity="sha256-rQq4Fxpq3LlPQ8yP11i6Z2lAo82b6ACDgd35CKyNEBw=" crossorigin="anonymous"/>

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</head>
<body>
<div id="map"></div>
<script>
  var wkt = 'LineString( 120 30 , 121 31 ,121 32 ,122 33 )';

  var format = new ol.format.WKT();

  var feature = format.readFeature(wkt, {});

  // 将方向标注放在线段中间
  function direction_labeling_02(res, lineStringForl, coordis, vs, styles) {
    for (let i = 0; i < vs.length; i++) {
      let line = vs[i]['line'];
      let start =line[0];
      let end = line[1];
      let array_coor = [
        (start[0]+end[0])/2, (start[1]+end[1])/2
      ];
      let d = vs[i]['d'];

      styles.push(new ol.style.Style({
        geometry: new ol.geom.Point(array_coor),
        image: new ol.style.Icon({
          src: 'http://localhost:9999/titles/fx.png',
          anchor: [0.75, 0.5],
          rotateWithView: true,
          rotation: -d
        })
      }))
    }


  }


  function direction_labeling_01(res, lineStringForl, coordis, vs, styles) {
// 这个地方可以修改成你要的箭头数量
    let arrow_count = res * 1.0 * 40;

    for (let i = 0; i < arrow_count; i++) {
      // 求坐标
      let array_coor = lineStringForl.getCoordinateAt(i * 1.0 / res);

      // // array_coor 在 coordis 不显示
      if (inc(coordis, array_coor)) {
        console.log("相同" + i);
        continue;
      }
      let rat = calcLinePointD(vs, array_coor);

      // 根据 array_coor 在那一条线段上设置 旋转角度
      styles.push(new ol.style.Style({
        geometry: new ol.geom.Point(array_coor),
        image: new ol.style.Icon({
          src: 'http://localhost:9999/titles/fx.png',
          anchor: [0.75, 0.5],
          rotateWithView: true,
          rotation: -rat
        })
      }));
    }
  }

  /**
   *
   * @param feature feature
   * @param res 总共多少个箭头
   * @returns {ol.style.Style[]}
   */
  function styleFunction(feature, res) {
    var lineStringForl = feature.getGeometry();

    var coordis = lineStringForl.getCoordinates();

    var styles = [
      new ol.style.Style({
        stroke: new ol.style.Stroke({
          color: '#23218b',
          width: 10
        })
      })
    ];

    // 计算线段角度
    let vs = calcLineStringD(coordis);
    // direction_labeling_01(res, lineStringForl, coordis, vs, styles);
    direction_labeling_02(res, lineStringForl, coordis, vs, styles);

    return styles;
  }

  // 计算点是否在线上
  function pointInLine(line, Q) {

    let pi = line[0];
    let pj = line[1];

    if ((Q[0] - pi[0]) * (pj[1] - pi[1]) == (pj[0] - pi[0]) * (Q[1] - pi[1]) && Math.min(pi[0], pj[0])
        <= Q[0] && Q[0] <= Math.max(pi[0], pj[0]) && Math.min(pi[1], pj[1]) <= Q[1] && Q[1] <= Math.max(pi[1],
            pj[1])) {
      console.log("再线段上");
      return true;
    } else {
      console.log("不再线段上");
      return false;
    }

  }

  // 返回点所在线段的具体角度
  function calcLinePointD(vs, point) {
    for (let i = 0; i < vs.length; i++) {
      let line = vs[i]['line'];
      let d = vs[i]['d'];
      if (pointInLine(line, point) == true) {
        return d;
      }
    }
  }

  // 计算线段角度
  function calcLineStringD(coordis) {
    let n = coordis.length;
    let vs = [];
    for (let i = 0; i < n; i++) {
      if (i + 1 < n) {
        vs.push({
          "line": [coordis[i], coordis[i + 1]],
          "d": calcD(coordis[i], coordis[i + 1])
        })
      }
    }
    return vs;
  }

  // 计算线段角度
  function calcD(start, end) {
    let dx = end[0] - start[0];
    let dy = end[1] - start[1];
    let rotation = Math.atan2(dy, dx);
    console.log("角度" + rotation);
    return rotation;
  }

  /**
   * 判断坐标组合cood中是否有atc,
   * 不会判断强写
   * @param cood 坐标组合
   * @param atc 坐标
   * @returns {boolean}
   */
  function inc(cood, atc) {
    for (c in cood) {
      if (cood[c][0] == atc[0] && cood[c][1] == atc[1]) {
        return true;
      }
    }
    return false;
  }

  var vector = new ol.layer.Vector({
    source: new ol.source.Vector({
      features: [feature]
    }),
    style: styleFunction(feature, 100)
  });
  var gaodeMapLayer = new ol.layer.Tile({
    source: new ol.source.XYZ({
      url: 'http://wprd0{1-4}.is.autonavi.com/appmaptile?lang=zh_cn&size=1&style=7&x={x}&y={y}&z={z}'
    })
  });

  var map = new ol.Map({
    layers: [gaodeMapLayer, vector],
    view: new ol.View({
      center: [120, 30],
      projection: 'EPSG:4326',
      zoom: 5
    }),
    target: 'map'
  });
</script>
</body>
</html>
